1. Field of the Invention
The present invention relates to a method and device for touch detection, and more particularly, to a method and device for parallel-scanning differential touch detection.
2. Description of the Prior Art
Referring to FIG. 1A, a schematic diagram depicting conventional touch detecting device 100. Display 110 is disposed under touch panel 120. Touch panel 120 has a plurality of first axial wires 122 and a plurality of second axial wires 124. First and second axial wires 122 and 124 are operatively coupled to driving/detecting unit 130. In this device, display 110 and touch panel 120 are integrated together in a conventional manner, and touch panel 120 consists of a plurality of layers that include a first layer of wires (not shown) having first axial wires 122 and a second layer of wires (not shown) having second axial wires 124. First and second axial wires 122 and 124 are parallel and electrical isolated from each other, and the first and second layers of wires are stacked onto and electrically isolated from each other. This part of the structure is well known in the art, and will not be further explained.
When touch detection device 100 is operating, driving/detecting unit 130 drives first or second axial wires 122 or 124 and detects variations in voltage, current or capacitance thereof to determine possible touch points. However, when examining the relationship between display 110 and touch panel 120 along cross-sectional line AA′, some noises can be found between them, as shown in FIG. 1B. In FIG. 1B, there are noises of stray capacitances between first axial wires 122 (only the first axial wires are described herein for illustration purposes) and display 110, for example: N1, N2, N3. When first axial wire 122 is being detected, the corresponding noises may reduce the sensitivity in detecting the first axial wire 122, or cause detection errors of touch points. Referring further to FIG. 1C, a schematic diagram depicting the variations in noises between touch panel 120 and display 110 under influences of different external forces is shown. Since the external forces exerted on touch panel 120 are not consistent, the distances between touch panel 120 and display 110 are not exactly the same. Therefore, noises N4, N5, N6 of stray capacitances will also be different in magnitude. This increases the difficulty in detection of touch panel 120.
Accordingly, the present invention provides a method and device for parallel-scanning differential touch detection, which overcomes the issues about noises between a conventional display and a touch panel and increases accuracy in detection of touch detection devices.